The present invention relates to apparatus and method for detecting an electromagnetic wave source which can detect and identify the position of the source of an unwanted electromagnetic wave (electromagnetic disturbing wave) in an electronic apparatus such as a product mounting various kinds of electronic parts on a printed board, as well as system and method for analyzing an electromagnetic wave source which can analyze whether the standards of VCCI (Voluntary Control Council for Interference by Information Technology Equipment) are satisfied.
Electromagnetic interference due to an unwanted electromagnetic wave occurs frequently concomitantly with the recent widespread use of information communication apparatus and the like and therefore, in unwanted electromagnetic radiation suppressing technology, a technique has been required which can detect a source in order to suppress the unwanted electromagnetic wave (electromagnetic disturbing wave) which is the cause of the electromagnetic interference.
Exemplified as conventional techniques concerning the method for detection of an electromagnetic wave source are xe2x80x9cA Proposal for Searching for Electromagnetic Wave Sources by Using a Synthetic Aperture Techniquexe2x80x9d by Junichi Kikuchi et al, Transactions of the Institute of Electronic Information and Communication Engineers of Japan, B-II, October 1985 (prior art 1), xe2x80x9cSearch for Electromagnetic Wave Sources by Using Maximum Entropy Methodxe2x80x9d by Junichi Kikuchi et al, Transactions of the Institute of Electronic Information and Communication Engineers of Japan, B-II, September 1986 (prior art 2), xe2x80x9cElectromagnetic Field Measurement and Numerical Analysis for EMC Problemsxe2x80x9d by Co-se Hayashi, NEC Techniques, September 1993 (prior art 3) and JP-A-4-329376 (prior art 4).
In the prior art 1, minute mono-pole antennas serving as electric field probes are arrayed along a Cartesian coordinate system on a plane at intervals of about xc2xc of the wavelength to obtain a result equivalent to the measurement of an unwanted electromagnetic wave using an aperture-front antenna equal to the array area. A position on the aperture front where an electromagnetic wave source exist is identified from a phase shift of the measured value and the operation time can be shorter than that in other techniques and values of both the magnitude and phase can be detected, but there arises a problem that the resolution is rough, amounting up to about xc2xc of the wavelength.
In the prior art 2, the maximum entropy method is applied to time-series information of electromagnetic wave measured continuously for a constant time to provide a power spectrum which in turn is made to correspond to the position of an electromagnetic wave source in two-dimensional space. While the positional accuracy is high to advantage, there arise problems that measurement must continue for the constant time or more, phase information of the source cannot be detected and a remote field cannot be determined through calculation.
In the prior art 3, an electromagnetic wave source area is divided into minute gratings, simultaneous equations of current and magnetic field are set up by using the same number of measuring values as that of grating points and the equations are solved to identify the electromagnetic wave source position. Given that the electromagnetic wave source exists on the minute grating and the measuring value is stringently correct, the position can be obtained in the form of a point and true values of the magnitude and phase can be obtained. But, if at least one of the factors contains an error, then there will arise problems that the simultaneous equations do not converge and any solution cannot be obtained or quite an erroneous solution is calculated.
In the prior art 4, an electromagnetic field radiated from an electromagnetic radiation source is measured by a stationary reference antenna and a movable measuring antenna, the amplitude of an electromagnetic field received by the measuring antenna and the phase difference between electromagnetic fields measured by the reference antenna and measuring antenna are used to provide a presumptive expression concerning distribution of electromagnetic disturbing sources and the position of an electromagnetic disturbing source is presumed by a spatial differential value of the presumptive expression. Accordingly, there arises a problem that unless the number of measuring points measured by the measuring antenna is considerably large, a point where the spatial differential value becomes large cannot be found and the accuracy of presumption is degraded.
The present invention contemplates solving the above problems and an object of the present invention is to provide electromagnetic wave sources detecting apparatus and method which can detect and identify a source of unwanted electromagnetic wave (electromagnetic disturbing wave) existing at an arbitrary position on an object to be measured with high accuracy and at a high rate by using a relatively small number of measuring points for the purpose of suppressing the electromagnetic field at a remote location from the apparatus.
Another object of the invention is to provide electromagnetic wave source analyzing system and method which can analyze and decide whether the measured object satisfies the VCCI standards.
Still another object of the invention is to provide electromagnetic wave source analyzing system and method which can survey factors of a source of unwanted electromagnetic wave (electromagnetic disturbing wave) detected on the measured object.
To accomplish the above objects, an electromagnetic wave source detecting apparatus according to the invention comprises a plurality of probes for measuring intensities Hm (inclusive of phase data) of an electromagnetic field generated from an object to be measured of an electronic apparatus at each measuring position (xm, ym) which changes two-dimensionally along a measured object plane near the measured object, and calculation means for calculating a phase difference xcex94xcfx86m=(xcfx862xe2x88x92xcfx861)m or time difference xcex94tm=(t2xe2x88x92t1)m between magnetic fields associated with the probes from the electromagnetic field intensities Hm measured by the individual plural probes at each measuring position (xm, ym), calculating a difference d between distances from a presumptive electromagnetic wave source on the basis of the phase difference or time difference calculated at each measuring position, determining a locus of the presumptive electromagnetic wave source on the measured object plane from the distance difference d and geometrical relations (for example, z1, z2) of the plurality of probes to the measured object and detecting an intersection of loci of the presumptive electromagnetic wave source which are determined at a plurality of measuring positions to calculate and identify a position (x5, ys)n of an electromagnetic wave source existing in the measured object.
Further, an electromagnetic wave source detecting apparatus according to the invention comprises a plurality of probes for measuring intensities Hm (inclusive of phase data) of an electromagnetic field generated from an object to be measured of an electronic apparatus at each measuring position (xm, ym) which changes two-dimensionally along a measured object plane near the measured object, and calculation means for calculating a phase difference xcex94xcfx86m=(xcfx862xe2x88x92xcfx861)m or time difference xcex94tm=(t2xe2x88x92t1)m between magnetic fields associated with the probes from the electromagnetic field intensities Hm measured by the individual plural probes at each measuring position (xm, ym), calculating a difference d between distances from a presumptive electromagnetic wave source on the basis of the phase difference or time difference calculated at each measuring position, determining a locus of the presumptive electromagnetic wave source on the measured object plane from the distance difference d and geometric relations (for example, z1, z2) of the plurality of probes to the measured object, detecting an intersection (xs, ys)n of loci of the presumptive electromagnetic wave source which are determined at a plurality of measuring positions to calculate and identify a position of an electromagnetic wave source existing inside the measured object, and further calculating magnitude In of current in the electromagnetic wave source existing at the identified position on the basis of the electromagnetic field intensities Hm measured by the probes at each measuring position.
Further, an electromagnetic wave source detecting apparatus according to the invention comprises a plurality of probes for measuring intensities Hm of an electromagnetic field generated from an object to be measured of an electronic apparatus at each measuring position (xm, ym) which changes two-dimensionally along a measured object plane near the measured object, and calculation means for calculating a phase difference xcex94100 =(xcfx862xe2x88x92xcfx861)m or time difference xcex94tm=(t2xe2x88x92t1)m between magnetic fields associated with the probes from the electromagnetic field intensities Hm measured by the individual plural probes at each measuring position, calculating a difference d between distances from a presumptive electromagnetic wave source on the basis of the phase difference or time difference calculated at each measuring position, determining a locus of the presumptive electromagnetic wave source on the-measured object plane from the distance difference d and geometrical relations (for example, z1, z2) of the plurality of probes to the measured object, detecting an intersection (xs, ys)n Of loci of the presumptive electromagnetic wave source which are determined at a plurality of measuring positions to calculate and identify a position of an electromagnetic wave source existing inside the measured object, and further calculating magnitudes In of current distributions in a plurality of electromagnetic wave sources existing at individual plural positions identified similarly on the basis of the electromagnetic field intensities Hm measured by the probes at each measuring position.
Further, in the present invention, the plurality of probes in the electromagnetic wave source detecting apparatus are arranged on the same probe axis at the individual measuring positions.
Further, in the present invention, the plurality of probes in the electromagnetic wave source detecting apparatus are arranged on the same probe axis vertical to the measured object plane at the individual measuring positions (xm, ym). In this case, the locus of the presumptive electromagnetic wave source on the measured object plane is indicated by a radius am.
Further, in the present invention, the calculation means of the electromagnetic wave source detecting apparatus further calculates inversely an electromagnetic field intensity En at a desired remote distance on the basis of the calculated magnitude of a current distribution in the electromagnetic wave source existing at the identified position on the measured object.
Further, in the present invention, the calculation means of the electromagnetic wave source detecting apparats inversely calculates an electromagnetic field intensity En at a desired remote distance on the basis of the calculated magnitude of a current distribution in each of the plurality of electromagnetic wave sources existing at each of the identified plural positions on the measured object.
Further, an electromagnetic wave source analyzing method according to the invention collates a position of an electromagnetic wave source existing on a measured object identified by using the aforementioned electromagnetic wave source detecting apparatus with mounting information (for example, circuit diagrams or mounting diagrams) of the measured object through, for example, display on a display unit. This permits electronic parts generating an unwanted electromagnetic wave (electromagnetic disturbing wave) to be ascertained.
Further, an electromagnetic wave source analyzing method according to the invention analyzes whether an electromagnetic field intensity at a desired remote distance calculated by using the electromagnetic wave source detecting apparatus satisfies the VCCI standards.
Further, an electromagnetic wave source detecting method according to the invention comprises measuring intensities Hm of an electromagnetic field generated from an object to be measured of an electronic apparatus at each measuring position (xm, ym) which changes two-dimensionally along a measured object plane near the measured object by using a plurality of probes, calculating a phase difference xcex94xcfx86m=(xcfx862xe2x88x92xcfx861)m or time difference xcex94tm=(t2xe2x88x92t1)m between magnetic fields associated with the probes from the magnetic field intensities Hm measured at each measuring position (xm, ym), calculating a difference d between distances from a presumptive electromagnetic wave source on the basis of the phase difference or time difference calculated at each measuring position, determining a locus of the presumptive electromagnetic wave source on the measured object plane from the distance difference d and geometrical relations (for example, z1, z2) of the plurality of probes to the measured object, and detecting an intersection (xs, ys)n of loci of the presumptive electromagnetic wave source which are determined at a plurality of measuring positions to calculate and identify a position of an electromagnetic wave source existing inside the measured object.
Further, an electromagnetic wave source detecting method according to the invention comprises measuring intensities Hm of an electromagnetic field generated from an object to be measured of an electronic apparatus at each measuring position (xm, ym) which changes two-dimensionally along a measured object plane near the measured object by using a plurality of probes, calculating a phase difference xcex94xcfx86m=(xcfx862xe2x88x92xcfx861)m or time difference xcex94tm=(t2xe2x88x92t1)m between magnetic fields associated with the probes from the electromagnetic field intensities Hm measured at each measuring position, calculating a difference d between distances from a presumptive electromagnetic wave source on the basis of the phase difference or time difference calculated at each measuring position, determining a locus of the presumptive electromagnetic wave source on the measured object plane from the distance difference d and geometrical relations (for example, z1, z2) of the plurality of probes to the measured object, detecting an intersection (xs, ys)n of loci of the presumptive electromagnetic wave source which are determined at a plurality of measuring positions to calculate and identify an electromagnetic wave source existing inside the measured object, and further calculating magnitude In of current in the electromagnetic wave source existing at the identified position on the basis of the electromagnetic field intensities measured by the probes at each measuring position.
As described above, with the construction as above, by approaching only magnetic field probes small enough not to disturb magnetic fields from the main body of the measuring apparatus to the measured object, the positions of electromagnetic wave sources existing at arbitrary positions on the measured object can be presumed from the phase information by reducing the number M of measuring points of magnetic field distribution without being affected by the influence of reflection to obtain the number N (=M) of the sources, thereby ensuring that the positions of the electromagnetic wave sources existing at the arbitrary positions can be presumed with high accuracy and at a high rate.
Further, with the above construction, it can be analyzed and decided whether the measured object satisfies the VCCI standards.
Further, with the above construction, factors (kinds of electronic parts) of the source of unwanted electromagnetic wave (electromagnetic disturbing wave) detected on the measured object can be surveyed.